1. Field of the Invention
The present invention relates to a waste disposal plant and, in particular, to a waste disposal plant utilizing a plasma arc torch to dispose of solid waste, waste in a solid container, granular waste, liquid waste, and mixtures thereof.
2. Discussion of the Prior Art
The daily generation of solid wastes is a fact of life in industrialized society and their disposal is becoming an ever-increasing problem. In the search for non-polluting, more efficient and less costly disposal, energy from waste (EFW) technologies are being developed such as gasification by means of a plasma arc torch in an enclosed, refractory lined, reactor vessel.
Plasma gasification is a non-incineration thermal process which uses extremely high temperatures in an oxygen starved environment to completely decompose input waste material into very simple molecules. The extreme heat and lack of oxygen results in pyrolysis of the input waste material, as opposed to incineration of those materials. Pyrolysis is the thermal decomposition of matter in the absence of oxygen. The by-products of the pyrolysis process are usually a combustible gas and an inert slag.
The heat source in a plasma gasification system is a plasma arc torch, a device which produces a very high temperature plasma gas. The plasma arc centerline temperature can be as high as about 50,000.degree. C., and the resulting plasma gas has a temperature profile of between about 3,000.degree. and about 8,000.degree. C.
A plasma gasification system is designed specifically for the type, size and quantity of waste material which must be processed. A refractory lined reactor vessel is preheated to a minimum wall temperature of approximately 1100.degree. C. before any processing commences, the actual minimum ambient temperature being determined by the waste material being processed. The very high temperature profile of the plasma gas then provides an optimum processing zone within the reactor vessel through which all input waste material is forced to pass. The reactor vessel operates effectively at atmospheric pressure. In this environment, all of the volatile input material is completely decomposed, while non-volatile input material, such as glass, metals, dirt, sand and the like melt to form slag. When cooled the slag form an inert solid mass. Thus, pyrolysis through plasma gasification provides for virtual complete gasification of all volatiles in the source material, while non-combustible material is reduced to an inert slag.
With municipal solid waste as the input waste material, the product gas and slag have very distinct characteristics. The product gas is high in hydrogen and carbon monoxide, with traces of methane, acetylene and ethylene. Therefore, the product gas from the pyrolysis of municipal solid waste be combusted very efficiently resulting in carbon dioxide and water vapor constituting the majority of the gaseous combustion by-product that is exhausted to the atmosphere. The slag is typically a homogeneous, silico-metallic mass, which is monolithic in texture, and with leachate toxicity levels orders of magnitude lower than those of current landfill regulations.
Plasma gasification systems offer considerable versatility as to throughput capacity. Plasma arc torches are available commercially in sizes ranging from 50 KW to over 60 MW; therefore, plasma gasification systems can be implemented at virtually any size capacity. The reactor vessel and plasma arc torch are specifically sized to the type and quantity of waste material to be processed. There are many plasma arch torch manufacturers who could provide equipment for use in such systems. Individual torches can be selected to operate in particular waste processing applications where their operational capabilities can be best applied.
Applicants' U.S. Pat. No. 5,280,757 which was issued Jan. 25, 1994 describes plasma gasification of waste, and is incorporated herein by reference.
Alvi et al. (U.S. Pat. No. 5,319,176) teaches a system for plasma gasification of gas which is limited to only a liquid or granular waste stream. It does not teach material processing apparatus for processing a variety of waste material such as municipal solid waste, boxed biomedical waste, granular contaminated solid, and liquid toxic waste. In addition, it does not teach the use of a platform located within the reactor vessel for initially receiving and holding such waste from the feed mechanism for thermal decomposition of such waste while on the platform by a plasma arc torch. In addition, it does not teach a specific barrier system.
Eshleman (U.S. Pat. No. 5,417,170) teaches a material processing apparatus, it neither teaches nor suggests an active feed mechanism.
U.S. relating to waste disposal vessels are Cline, et al. (U.S. Pat. No. 4,989,522) and Holden et al. (U.S. Pat. No. 5,095,828). Other prior art patents relating to waste incineration and gasification plants are Blankenship (U.S. Pat. No. 4,495,873); Ritter (U.S. Pat. No. 5,062,372); Nance et al. (U.S. Pat. No. 5,101,739); Wong et al. (U.S. Pat. No. 5,288,969); Maeda et al. (U.S. Pat. No. 5,295,449); Eshleman (U.S. Pat. No. 5,361,709); Shlienger (U.S. Pat. No. 5,410,121); and Foldyna et al. (U.S. Pat. No. 5,477,790).
None of these references teaches a plasma arc gasification plant which is useful for efficiently and safely processing many kinds of waste, such as municipal solid waste, boxed waste, liquid waste and granular waste in a manner which avoids environmental contamination. None of these references teaches a plasma arc gasification plant having a platform located Kin the reactor vessel for initially receiving waste from the feed mechanism for thermal decomposition of such waste by a plasma arc torch. In addition, none of these references teaches a specific barrier system which is neither taught nor suggested by Alvi et al. By contrast, the present patent application, as amended, claims an active feed mechanism.